fuse utimensat problem

Question

Hi. I am developing fuse fs at python (with fuse-python bindings). What method I need to implement that touch correctly work? At present I have next output:

$ touch m/My\ files/d3elete1.me 
touch: setting times of `m/My files/d3elete1.me': Invalid argument

File exists "d3elete1.me":

$ ls -l m/My\ files/d3elete1.me 
-rw-rw-rw- 1 root root 0 Jul 28 15:28 m/My files/d3elete1.me

Also I was trying to trace system calls:

$ strace touch m/My\ files/d3elete1.me
...
open("m/My files/d3elete1.me", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK|O_LARGEFILE, 0666) = 3
dup2(3, 0)                              = 0
close(3)                                = 0
utimensat(0, NULL, NULL, 0)             = -1 EINVAL (Invalid argument)
close(0)                                = 0
...

As you see utimensat failed. I was trying to implement empty utimens and utime but its are not even called.

Answer 1

You must implement utimens and getattr. Not all the system calls necessarily map directly to the C calls you might be expecting. Many of them are used internally by FUSE to check and navigate your filesystem, depending on which FUSE options are set.

I believe in your case FUSE is preceding it's interpretation of utimesat to utimens, with a getattr check to verify that the requested file is present, and has the expected attributes.

Update0

This is a great coincidence. There is a comment below suggestion that the issue likes with the fact that FUSE does not support utimensat. This is not the case. I had the exact same traceback you've provided while using fuse-python on Ubuntu 10.04. I poked around a little, it would appear that the fuse-python 0.2 bindings are for FUSE 2.6, it may be that a slight change has introduced this error (FUSE is now at version 2.8). My solution was to stop using fuse-python (the code is an ugly mess), and I found an alternate binding fusepy. I've not looked back, and had no trouble since.

I highly recommend you take a look, your initialization code will be cleaner, and minimal changes are required to adapt to to the new binding. Best of all, it's only one module, and an easy read.

Answer 2

Try launching fuse with the -f option. Fuse will stay in foreground and you can see errors in the console.